Influence of desalivation in rats on incidence of caries in intact cagemates.

The evidence that dental caries is an infectious and transmitted disease in rodents is unequivocal. However, the factors controlling the transmission of micro-organisms from one animal to another have not been extensively explored. Results from previous studies in our laboratory showed that desalivated animals became infected by Streptococcus sobrinus in a shorter period of time than did intact animals. Furthermore, an additional study in our laboratory showed that animals with intact salivary function caged with desalivated animals harbored more S. sobrinus immediately following establishment of infection than did intact animals housed with other intact animals. Therefore, it seemed appropriate to determine the influence on caries development of caging a desalivated animal with an intact animal. In this study, intact Sprague-Dawley rats were caged with desalivated animals; additional groups of intact animals were housed with chlorhexidine-treated animals that were either intact or desalivated. Although chlorhexidine suppressed both caries development and the level of infection by S. sobrinus, nevertheless, intact animals caged with desalivated animals invariably developed more caries than did intact animals housed with other intact animals. Treating intact animals with chlorhexidine did not affect caries scores in untreated intact cagemates. Overall, the results suggest that a highly acidogenic flora with enhanced virulence (including S. sobrinus) is selected in the desalivated animals; this flora is apparently readily transmitted to intact cagemates, leading to enhanced levels of smooth-surface caries.

Enhancing the virulence of Streptococcus sobrinus in rats.

The purpose of this study was to explore the virulence of strains of Streptococcus sobrinus that had been re-isolated from a desalivated rat. Furthermore, we wished to determine the influence of desalivation on the acidogenicity of fasting and sucrose-pulsed dental plaque in rats infected by strains of S. sorbrinus. Experimental groups were formed and infected as follows: Group 1, desalivated animals, S. sorbrinus ATCC27352; Group 2, intact animals, infected as in Group 1; Group 3, desalivated animals, S. sorbrinus re-isolated from a desalivated animal that had been infected with the ATCC 27352 strain for five weeks; Group 4, intact animals, infected as in Group 3; Group 5, desalivated animals, S. sobrinus re-isolated from a desalivated animal that had been infected with the ATCC27352 strain for ten weeks; Group 6, intact animals, infected as in Group 5; Group 7, intact animals, no infection. All animals were fed cariogenic diet 2000 and sucrose-sweetened drinking water ad libitum. After five weeks, desalivated and intact animals that had been infected with isolates obtained from desalivated animals had significantly higher (p less than 0.05) smooth-surface-caries scores than did intact and desalivated animals infected with cultures of the original stock ATCC strain. Moreover, fasting plaque pH values were statistically lower in desalivated animals (Groups 1 and 3) than in intact animals (Groups 2, 6, and 7) (Turkey analysis, p less than 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)

Caries incidence in intact rats infected with Streptococcus sobrinus via transmission from desalivated cagemates.

The purpose of this study was to determine the influence of caging desalivated S. sobrinus-infected rats on the caries incidence in intact, previously uninfected cagemates. Weanlings were divided as follows: Stage I: Twenty desalivated animals paired with 20 intact animals (Group I); 20 intact animals paired with 20 intact animals (Group II). Animals were infected with S. sobrinus and fed diet 2000 and 10% sucrose water. After five weeks, ten paired animals from each group were killed. Desalivated animals had statistically higher (p less than 0.05) caries scores than did other animals. Stage II: The remaining Stage I infected animals from Groups I and II were paired with 40 new uninfected animals 15 days of age and fed cariogenic diets. After five weeks, new intact animals paired with Stage I desalivated animals had significantly higher smooth-surface enamel caries scores (38.0; SE 7.84) than new intact animals paired with Stage I intact animals (11.15; SE 3.69). Moreover, new intact animals caged for only five weeks with Stage I desalivated animals developed smooth-surface caries (38.0; SE 7.84) to a degree comparable with that in all Stage I intact animals in the experiment for ten weeks (36.6, SE 9.5; and 30.05, SE 4.1). The data suggest that desalivation may select a readily transmissible strain of S. sobrinus, which demonstrates enhanced virulence.

Effect of desalivation and age on susceptibility to infection by Streptococcus sobrinus.

The influence of desalivation and age on susceptibility to infection by Streptococcus sobrinus was studied using 80 Sprague-Dawley female rats weaned at age 21 days. Forty animals (donors) were infected with S. sobrinus 6715 (ATCC 27352), formed into ten groups of 4, fed diet 2000, and offered 10% sucrose water ad libitum. The remaining 40 animals were fed laboratory chow and sterile distilled water until introduced into the experiment. When the animals were aged 25 days, 10 noninfected animals were anesthetized, desalivated, and caged with 10 infected (donor) animals (group I). On day 36 these procedures were repeated on the remaining animals (group II). Infection was checked daily. Animals were regarded as infected when S. sobrinus was detected on 2 consecutive days and confirmed 1 week later. Animals were killed, jaws dissected, and populations of S. sobrinus and total bacterial viable count of each jaw estimated. The average number of days from pairing to detecting infection (2 consecutive days) was as follows: group I (age 25 days): desalivated 5.4 (SD 2.5), intact 8.8 (SD 4.5); group II (age 36 days): desalivated 7.8 (SD 2.9). Only 3 intact animals became infected in group II after a total elapsed time of 21 days. The mean viable counts of S. sobrinus per jaw in group 1 were as follows: desalivated 3.6 x 10(6) (SD 4.1); donor cagemate 13.0 x 10(6) (SD 9.7); intact 0.26 x 10(6) (SD 0.39); donor cagemate 4.5 x 10(6) (SD 4.3). Desalivated animals tended to be more heavily infected than intact animals.(ABSTRACT TRUNCATED AT 250 WORDS)